Deirdre Fleming: Moose-gut studies help determine population’s health

For the second year, state biologists will be collecting cow moose gut piles — as many as they can get from the 750 hunters who have cow-only permits in northern Maine. The study is a new effort to determine the health of Maine’s moose population. And if it’s found to be very healthy, it could mean an increase in moose permits.

“The moose permits have been very conservative,” said Maine moose biologist Lee Kantar. “We have other measures that allow us to manage the moose population. But we have been the only Northeast state that has not collected cow moose reproductive organs annually and routinely.”

Maine used to collect cow reproductive organs from hunter-tagged moose back when the moose season was held at different times in northern Maine.

From 1980 to 1989, biologists collected samples and the valuable data that came with them. But the Legislature changed the dates of the moose hunt, and in northern Maine, where cow permits are given out, the hunt was not late enough to gather the reproductive data because the moose were not yet breeding at the time of the hunt.

For the cow ovaries to show how many calves the cow is able to carry, or its ovulation rate, the moose have to be breeding.

The study was reintroduced in northern Maine last year, when the hunt was pushed back in those districts with cow permits.

Now Maine’s moose biologists have a great chance to determine whether Maine’s northern moose population is at a healthy size for the habitat available or if there is an opportunity to harvest more moose.

A similar study has been done with great success in Vermont, where biologists have collected cow reproductive organs from hunters since 1993.

The study helped biologists determine that the moose population had grown to well beyond the carrying capacity for the habitat in Vermont’s Northeast Kingdom, said Vermont moose biologist Cedric Alexander.

“The literature through the last 50 years of wildlife management shows moose ovulation-rate studies are one of the best indicators as to whether moose are at the carrying capacity, below it or above it,” said Alexander in St. Johnsbury, Vt.

The study shows the rate at which cows are ovulating. If they are in robust health, the reproductive organs collected will show an ovulation rate of 1.4 (meaning the moose has the potential to bear one to two calves), Alexander said. But as the study in Vermont showed, if there are too many moose on the landscape and trees are getting over-browsed and food is scarce, the reproductive rate in cows can drop to less than one calf per adult cow.

When the study started in Vermont, moose had an average ovulation rate of 1.4 calves for a prime breeding age cow. That’s a healthy ovulation rate, Alexander said, with half the cows giving birth to twin calves.

But as the moose population began growing in northeast Vermont, many signs pointed to there being too many moose for the habitat.

Yearling moose tagged by hunters had dropped in size, from an average weigh of 469 pounds to 418 pounds in 2009. And the ovulation rate shown through the reproductive organs, or gut piles, had dropped from 1.4 to 0.86 in 2009.

“That is one of the lowest ovulation rates recorded in 15 to 20 such studies in North America,” Alexander said.

So the Vermont Fish & Wildlife Department bumped up permits to 1,200 two years ago and saw immediate results: Ovulation rates in hunter-killed cows increased to 1.13 in 2010.

And yearling moose weights jumped back up to an average of 435 pounds last year.

“It’s amazing how many moose we had out there,” Alexander said.

The information gathered through the gut piles was key in knowing how crowded moose were in the Northeast Kingdom. And the long-standing study now has plenty of participation by hunters, Alexander said.

In Maine, Kantar is hoping for the same.

“The bottom line is moose belong to the people of Maine up until it gets that green (tagging station) plastic seal, then it is the possession of the hunter. The collection of the data benefits all the people in the state of Maine,” Kantar said.

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